#! /usr/bin/env python
#
def r8row_swap ( m, n, a, irow1, irow2 ):

#*****************************************************************************80
#
## R8ROW_SWAP swaps two rows of an R8ROW.
#
#  Discussion:
#
#    An R8ROW is an M by N array of R8's, regarded as an array of M rows,
#    each of length N.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    28 February 2016
#
#  Author:
#
#    John Burkardt
#
#  Parameters:
#
#    Input, integer M, N, the number of rows and columns.
#
#    Input, real A(M,N), the R8ROW.
#
#    Input, integer IROW1, IROW2, the two rows to swap.
#    0 <= IROW1, IROW2 < M.
#
#    Output, real A(M,N), the array after row swapping.
#
  from sys import exit

  if ( irow1 < 0 or m <= irow1 ):
    print ''
    print 'R8ROW_SWAP - Fatal error!'
    print '  IROW1 is out of range.'
    exit ( 'R8ROW_SWAP - Fatal error!' )

  if ( irow2 < 0 or m <= irow2 ):
    print ''
    print 'R8ROW_SWAP - Fatal error!'
    print '  IROW2 is out of range.'
    exit ( 'R8ROW_SWAP - Fatal error!' )

  if ( irow1 == irow2 ):
    return a

  for j in range ( 0, n ):
    t          = a[irow1,j]
    a[irow1,j] = a[irow2,j]
    a[irow2,j] = t

  return a

def r8row_swap_test ( ):

#*****************************************************************************80
#
## R8ROW_SWAP_TEST tests R8ROW_SWAP
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    28 February 2016
#
#  Author:
#
#    John Burkardt
#
  import numpy as np
  from r8row_print import r8row_print

  m = 3
  n = 4

  print ''
  print 'R8ROW_SWAP_TEST'
  print '  R8ROW_SWAP swaps two rows of an R8ROW.'

  a = np.zeros ( [ m, n ] )

  k = 0
  for i in range ( 0, m ):
    for j in range ( 0, n ):
      k = k + 1
      a[i,j] = k

  r8row_print ( m, n, a, '  The original matrix:' )

  row1 = 0
  row2 = 2

  print ''
  print '  Swap rows %d and %d' % ( row1, row2 )

  a = r8row_swap ( m, n, a, row1, row2 )

  r8row_print ( m, n, a, '  The modified matrix:' )
#
#  Terminate.
#
  print ''
  print 'R8ROW_SWAP_TEST:'
  print '  Normal end of execution.'
  return

if ( __name__ == '__main__' ):
  from timestamp import timestamp
  timestamp ( )
  r8row_swap_test ( )
  timestamp ( )